Segmental innervation of the skin (dave's notes)

Question 1

How much do adjacent dermatomes overlap

Answer 1

Considerably

Question 2

Skin that envelops a limb is drawn out from the trunk. What does this result in?

Answer 2

Missing dermatomes that create an axial line

Question 3

Give the anterior axial line of the upper limb

Answer 3

From sternal angle, 2nd costal cartilage, down the front of the wrist

Question 4

Give the posterior axial line of the upper limb

Answer 4

From the vertebral prominens to the insertion of deltoid

Question 5

What happens to the axial lines of the lower limb?

Answer 5

They are distorted from foetal rotation and a degree of borrowed skin???

Question 6

What is the anterior axial line of the lower limb?

Answer 6

Spirals from the root of the penis, across the front of the scrotum, thigh, calf, achilles

Question 7

What is the posterior axial line of the lower limb?

Answer 7

From the 4th lumbar interspace in a bold convexity, across buttock, thigh, head of fibular, and halfway down the calf

Question 8

The central root of each limb plexus is the most ……………… .

Answer 8

Peripheral

Question 9

Each anterior ramus through a limb plexus is paid off into ……….

Answer 9

Appropriate cutaneous nerves

Question 10

What accompanies spinal nerves to the dermatome?

Answer 10

Sympathetic grey branches

Question 11

A “low” spinal anaesthesia anaesthetises the skin of the posterior 2/3rds of the scrotum but not the anterior 1/3rd. How much further up must the anaesthetic be to achieve this?

Answer 11

7 spinal segments higher up

Question 12

SEE PAGE 25 FOR DERMATOMES

Answer 12

SEE PAGE 25 FOR DERMATOMES